While a clean install is not always necessary, slightly better stability and performance can be expected when XP is installed to a clean hard drive or partition. The XP upgrade is a vast improvement over previous Windows upgrades, and is usually the best choice when transitioning from a previous Windows version to XP. I recommend the clean install approach as a last resort, not the first option. My recommendation is to prepare for a clean install, but first try the upgrade option. If in the unlikely event results of the upgrade are a failure, nothing is lost but the time spent doing the upgrade and evaluating the results. The preparation to clean install is in place and the upgrade experience will serve as a hands on tutorial to familiarize you with the XP setup procedure.